Intraoperative Neuromonitoring in Thyroid Surgery

Thyroid surgery carries a risk of injury to laryngeal nerves, notably the recurrent laryngeal nerve (RLN) and the external branch of the superior laryngeal nerve (EBSLN). Intraoperative neuromonitoring (IONM) has emerged as a pivotal adjunct to visual nerve identification, providing real-time feedback via electromyography (EMG) recordings. Intermittent stimulation helps to confirm nerve integrity during dissection, whereas continuous monitoring (cIONM) can detect impending nerve compromise by tracking amplitude and latency changes on the vagus nerve–RLN axis. The technique has evolved alongside innovations in tracheal tube electrodes and videolaryngoscopy guidance to ensure optimal placement of EMG endotracheal tubes. Globally, IONM has been adopted to reduce transient and permanent vocal cord palsy, guide risk stratification in anatomical variants such as the non-recurrent laryngeal nerve (NRLN) and minimise injury in reoperations. Clinical and meta-analytic evidence underscores its role in enhancing patient safety and functional outcomes, particularly in high-risk scenarios such as malignancy, reoperative fields or large goitres requiring extensive dissection.

Research from Nature Portfolio

Recent studies have examined the impact of advanced techniques on nerve monitoring efficacy. An observational study compared video and direct laryngoscopy during EMG tube placement, demonstrating that videolaryngoscopy significantly improved the percentage of glottic opening and Cormack–Lehane grade in the thyroid surgical position. Enhanced glottic view facilitated accurate electrode positioning, thereby reducing the risk of tube displacement and optimising signal quality. A foundational meta-analysis synthesised data from studies spanning nearly four decades to assess the protective effect of IONM on RLN injury. The analysis revealed a consistent reduction in total, transient and permanent nerve injuries when IONM was employed, with particular benefit in bilateral operations and malignancy cases. These findings consolidate the evidence base for routine neuromonitoring as a standard of care in thyroidectomy.

Intraoperative Neuromonitoring in Thyroid Surgery publication trend

The graph below shows the total number of articles in intraoperative neuromonitoring in thyroid surgery across all publications each year (not limited to Nature Index journals).

Technical terms

Intraoperative neuromonitoring (IONM): Real-time nerve assessment using electrical stimulation and electromyography to preserve neural function during surgery.

Continuous IONM (cIONM): Uninterrupted electrical stimulation of the vagus nerve to track ongoing changes in nerve signal amplitude and latency.

Electromyography (EMG): Recording of electrical activity in muscles, used to infer nerve integrity when captured via specialised endotracheal tube electrodes.

Recurrent laryngeal nerve (RLN): A branch of the vagus nerve that innervates most intrinsic muscles of the larynx, vulnerable during thyroid dissection.

Non-recurrent laryngeal nerve (NRLN): A rare variant of the RLN with a direct course from the vagus nerve to the larynx, associated with higher injury risk.

Videolaryngoscopy: Use of a video-enhanced laryngoscope to visualise the glottis for precise placement of EMG endotracheal tubes under surgical positioning.

References

1. Assessment of different classification systems for predicting the risk of superior laryngeal nerve injury during thyroid surgery: a prospective cohort study. Frontiers in Endocrinology (2023).
2. Continuous Intraoperative Nerve Monitoring of a Non-Recurrent Laryngeal Nerve: Real-Life Data of a High-Volume Thyroid Surgery Center. Cancers (2024).
3. Usefulness of video laryngoscopy in tracheal intubation at thyroid surgical position for intraoperative neuromonitoring. Scientific Reports (2024).
4. Safety of continuous intraoperative vagus nerve neuromonitoring during thyroid surgery. BJS Open (2023).
5. Protective Effects of Intraoperative Nerve Monitoring (IONM) for Recurrent Laryngeal Nerve Injury in Thyroidectomy: Meta-analysis. Scientific Reports (2018).